1. Field of the Invention
The present invention relates to an integrated system consisting of a fixed strand, a locking carabiner and a harness operable for enabling a person to descend from a height, and for lowering a person or object from a height.
2. Prior Art
The challenge of descending safely from a height can be traced back to prehistory, where archeological evidence of broken bones indicates, amongst other causes, trauma from falls. With the advent of the Industrial Revolution, came the development of strong, reliable cordage, which made the processes of descending (wherein the person is in control of the action) and lowering (wherein the person or object has no control over the action) significantly safer. But no matter how strong the strand (being any form of rope, webbing or cable), descending hand over hand posed a significant problem due to a lack of upper body strength—most people were not strong enough to support their weight for more than a few seconds. In addition, there was still the danger of falling off the strand, because the person descending was not attached to anything. Similarly, lowering techniques typically involved either lowering objects via a simple rope with no mechanical advantage which required significant muscle power and offered little control, or an arrangement mitigated by one or more pulleys, which were heavy to transport, difficult to rig, and slow to use.
Descending and lowering systems fall into two broad categories: those that make use of a fixed strand (wherein a device slides down a stationary strand) and those that do not. Since this application is for a system that makes use of a fixed strand, emphasis has been placed on an examination of similar systems and devices.
Before 1980, fixed-strand descending devices tended to be bulky (Hunter, 1976, U.S. Pat. No. 3,949,832) and complicated (Hobbs, 1972, U.S. Pat. No. 3,695,397 and Hobbs, 1973, U.S. Pat. No. 3,757,901). In the 1970's and 80's, developments in the sport of caving revolutionized fixed-strand descending technology resulting in off-the-shelf descending gear that was lighter, stronger and easier to use. Such descending gear, which lead to the sport of rappelling (also called abseiling), typically consists of a mountain climbing grade rope, a waist harness (such as disclosed by Petzl, 1992, U.S. Pat. No. 5,145,027), a locking carabiner (an oval of hardened metal with a lockable gate) and a friction device such as some variation of the popular “figure 8”, typically used for short rappels, or a brake bar (such as disclosed by Steffen, 1982, U.S. Pat. No. 4,311,218) for rappels over 200 feet. While rappelling allows the user to safely descend from height, it has a number of shortcomings. First, it is heavy. A typical rappelling configuration, consisting of a mountain climbing belt, 200 feet of 10.8 mm static mountaineering rope, a figure 8-type friction device and locking carabiner, as well as related gear, such as non-locking carabiners and webbing, weighs approximately 15 pounds. In the case of longer descents, the use of a rolling rack as a friction device instead of a “figure 8” type of device, could add an extra pound and a second belay line would add another three to five pounds. It is also bulky, and requires a large pack to carry all the rappelling gear mentioned above.
It is complicated and time consuming to rig. Rappelling is an unforgiving sport. There are strict conventions that have to be rigidly adhered to, or the procedure is not safe. Typically, two anchor points are selected, climbing-grade webbing made fast to each with a special non-slip knot, double non-locking carabiners placed on each webbing; the rope has to be looped and knotted with a special non-slip knot and affixed to all four carabiners. The harness has to be put on, buckled at the waist using a locking buckle, leg straps adjusted and tightened, rope run through the friction device, a locking carabiner must link the friction device with rope to the mountain climbing belt—all this before ever beginning the descent. Rigging a second line for the purposes of belaying (wherein a line is attached to the person descending, looped around an anchor point at height and then down to a person at a lower level who provides backup control of the descent with a second friction device) would add another level of complexity.
Rappelling equipment requires extensive training to use. The act of rappelling requires certain formal postures and procedures such as: the right hand gripping the rope in a manner that is relaxed yet firm, and simultaneously, the same right hand moving back and forth to different positions on the right hip, while at the same time, leaning far back, feet wide apart and knees locked. If any of these steps are left out, the rappeller could be at risk. With a simple belay device, such as a “figure 8”, there is not much latitude in adjusting the amount of friction, other than the amount of pull on the rope. Finally, during the act of rappelling, the right hand bears all the responsibility and effort of controlling the descent; the left hand is used only for stabilizing. This requires a certain amount of strength and agility.
A system similar to conventional rappelling uses a friction device in the form of a forged aluminum shank with a rope guide and attachment holes at each end and a metal cover, whereby the cover is removed, the rope is wrapped a number of times around the shank and then the cover is replaced. Such systems are marketed under trademarks such as Sky Genie, Frost Rope Rider and Miller Descent Device. While elegant in design, they are really just variations on the conventional rappelling system with a different sort of friction device, and thus share all the same drawbacks as rappelling mentioned above. The same drawbacks also apply to descending systems that make use of hand brakes consisting of wheels, pulleys, gears, sheaves and like mechanisms such as Rogelja, 1994, U.S. Pat. No. 4,596,314.
The prior art of fixed strand fire escape and evacuation systems suffers from the same drawbacks as the rappelling systems outlined above, namely: they are bulky (Sheppard, 1977, U.S. Pat. No. 4,024,927), and complicated (Green et al., 1990, U.S. Pat. No. 4,934,484 and Varner et al., 1991, U.S. Pat. No. 5,038,888). In addition, most are made with unrated materials (Budd, 1888, U.S. Pat. No. 386,237) or are potentially unsafe (such as the web-on-web design of Walker Sr., 1986, U.S. Pat. No. 4,588,045), and for that reason have questionable safety margins.
The device disclosed by Wood, 1982, U.S. Pat. No. 4,311,217 is one of only a few devices dedicated to lowering a person or object on a fixed rope. While it is elegant and compact, it suffers from the drawback of having a number of pins and hinges which add to the complexity of the design and are points of potential failure. The lack of prior art of fixed-strand lowering systems is in part due to the fact that the use of a fixed strand is not the conventional method of lowering—moveable strands with spools and pulleys are more the norm. Another reason is that some fixed-strand descending devices, such as Sky Genie, Frost Rope Rider and Miller Descent Device mentioned above, can also double as lowering devices. A drawback of such devices is that they consist of a number of components making them bulky and complicated to rig.